Incandescent electric lamp for projection purposes



Nov. '3, 1925. 1,560,265

D.LELY,JR

INCANDESCENT 'ELECTRIULAMP FOR PROJECTION PURPOSES Filed March so 1921 3 1. d d z Inventor 0216 j/flormeys,

Patented Nov. 3, 1925.

UNITED STATES r 1,560,265 PATENT OFFICE,

DIRK LELY, JIL, OF EINDHOVEN. NETHERLANDS. ASSIGNOR. BY MESNE ASSIGNMENTS,

TO GENERAL ELECTRIC COMPANY. OFSCHENECTADY. NEW

OF NEW YORK.

YORK. A CORPORATION Application filed March 30, 1921.

Serial No. 457,141.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3. 1921. 41 STAT. L.. 1313.)-

Be it known that l. l)1111 lmrv. Jr.. a subject of the Queen of the Netherlands. residing in l lindhoven. lrovince ol North lirabant. Kingdom (11' the Netherlands. have invented certain new and useful improvements in lneamleseent Iilertrie Lamps for Projection Purposes (for which I have tiled application in the Kingdom of the Netherlands on June 2nd. ltllT. Serial Number 8.286; in (lermany on lhwember 21st. 1917: in England on January H111. ltllis': in France on January 29th. 1911): in 'ltaly June It). 1920; and in (zechoslovakia on February 9th, 1921), and ot which the following is a specilication.

lllectrical incamlesrent lamps for projection purposes are preferably so arranged. thatthe greatest part of the light is emanated in the desired direction. All the rays not passing through the condenser are lost for the purpose. in a lamp whichburns econoinicall the proportion between the light emanated in the favourable (lll'ttlltill and the light totally emanated must of ne cra s-it be as large as possible.

The relative radiation in a certain direction is considel'abiv increased when the incandescent member has not the usualcircu; lar section but i very much tlattened,which may be done by shaping said member as :i band and not as a wire with circular section. 11' several of these band-shaped incandesctait members are provided adjacent to each other a source of light may be obtained which is approximately as favourable fonthe radia tion in one direction as a plain surface.

With a Hat ra'diating surface the luminous power. measured in a direction perpendicular to said surface, is just t\v.i=e as great as the mean spherical candle power.

As it is very dillicult to make band-shaped members, adapted for use in lamps usedt'or projectioi'i purposes. they are hardly ever applied in the lamps now on the market. The older lamps are generally provided with one or more incandescent members each consisting of a circular wire helically wound around a circular mandrel. The luminous power oleach of these. incandescent members. measured in the most favourable direction, is about 27% stronger than the mean flattened on the side. where the gr atesti ra- 1 diation is desired.

The invention also comprises a "ollstllh tion having an incandescent member. the outer coils of which are wound with smaller distances. between their convolutions than the more centrally situated parts.

In the accompanying drawings. which illustrate the invention by way of example only,

Fig. l is a l'ront elevation of a lamp, part ot the bulb being shown broken away.

l ig'. is a detailed view on a larger scale. showing the cross-section ot the incandescent coils at 2 2 in l"ig. l. and Fig. 3 is a detailed view on a larger scaliu showing the ditierent winding pitches ot' the coils.

in these drawings 1/ l/ are the leading-in wires fused into the glass of the bulb in the usual manner. and c is the incandescing tila .ment which is shown as coiled into four fiattened helices. of which the two inner ones 1/ (I are loosely coiled. as shown in Fig. 1). while the two outer ones 0 (a are. coiled more closely. f in Fig. l are the usual supporting wires.

l lvidently a lamp radiating a greater per centage of its light in the most favourable direction can very easily be manufactured by winding the circular avire heli*ally in such a way that the section of the incandescent Inemher ditlers considerably from a circular section.

This may be doneby winding a circular wire round a band-shaped mandrel, or by winding it round a circular mandrel, removing the latter and giving the spiral a flattened shape by rolling it.

The wire may also be wound about a band-shaped mandrel and the spiral thus obtained may afterwards be further flattened by rolling. 1

In doing so it will be clear that the wire is bent more in some places than in others,

the wire itself keeps its circular section and ma consequently be manufactured without di culty. Two or more of the incandescent members thus formed are placed adjacent to each other. A wire of 217 millionths of a meter (217 p.) may for instance be wound helically about a mandrel of 920 millionths of a meter (920 9.) width and 220 millionths of a meter (220 a) thickness.

A lamp constructed in this way has been found to have a horizontal luminous power 92% stronger than the mean spherical luminous power. Compared with an incandescent member consisting of a round spiral, the saving in consumption of current will be about 33%, the horizontal luminous powers of both lamps being the same.

In order to obtain the smallest possible surface and a uniform radiation it is desirable to place the different parts, of which the source of light consists, and which are generally provided in a perpendicular direction, as near to each other as possible.

- sequently in those lamps, wherein the source of light consists of morethan two parts, the

Con-

peripheral parts will radiate considerably more than the central parts of the radiating member, and will consequently be of lower temperature, which causes a somewhat unment and which in such cases becomes the light-emitting element instead of the filament.

\Vhat I claim is:

A metallic filament lamp for pro ection purposes comprising: naked incandescent filaments of circular cross-section wound into coils of flattened form, having the outer coils wound into'closer spirals than the more centrally situated coils.

In witness whereof, I have hereunto signed my name.

DIRK LELY, JR. 

